Kamen Rider Flux
by Kamen Rider Saisho
Summary: 2 years after the events of Back to the Future, Marty is visited by Doc once again. He has made major discoveries in their time apart, including creatures called Imagin. When the alternate Biff becomes one, Marty must stop him. Den-O Origin Story.


Disclaimer: I don't own Back to The Future or Kamen Rider. They are owned by Universal Studios and Toei Co., respectively.

Note: I do not take the 2010 back to the future game or the animated series from the '90s as canon to the movies.

**Kamen Rider Flux**

"Normal with Quotations" Is speech

'_Italicized with apostrophes'_ is thought (not italicized in flashbacks)

_Italicized text is flashbacks or a change in location/time period "with quotations for speech during flashback"_

**Bold text** is a narration

**Bold and underlined**__Is belt speech

**The year is 1987. It has been well over a year since Marty last saw Dr. Emmet Brown leave with his wife, Clara, and his two children, Jules and Verne, in the time-traveling train he built in 1885. Since then, Marty's life had (at least somewhat) stabilized. The Doc had not visited him or recruited him on any more missions to fix history, past, present, or future. Meanwhile, unbeknownst to Marty, the Doc has actually gone into the future they have created through their numerous adventures. In this future, the Doc has found a fellow researcher in the space-time continuum. He is known simply as "The Station Master." Together, the two have made a discovery that could end humanity as they know it.**

_Hill Valley, California, 1987_

Marty McFly sat on his front porch, staring at the street in front of him. He sighed and hopped down off the porch. He walked over to his truck, hopped in, and started driving. This summer, Marty had a part time job at, ironically, Biff's Auto Shop. Biff had become well known enough in hill valley to buy a new complex near Hilldale. Although it took longer, Marty always made a point to drive through the railroad tracks. He glanced and laughed at the stretch of straight track. They were still cleaning up bits of stainless steel from the DeLorean after more than a year. The light flashed and the bells rang as the barricade lowered. Marty looked down the tracks. No sign of a train from either side. Marty did a double take and confirmed there was no sign of a train. Making sure there was no one behind him, Marty backed up a few feet, turned off his truck, and got out. He jogged up to the barricade, anticipating what was to happen next. The air sparked three times in front of him and a huge grin spread across his face. He gripped the barricade as the air exploded and the time train rolled onto the tracks.

"DOC!" Marty screamed as he hopped the barricade. The door to the train opened and the stairs lowered. Doctor Emmet Brown ran down the steps, looking around frantically. Seeing Marty, the scientist smiled as he embraced his old friend.

"Doc it's so good to see you! What are you doing in 1985? Where's Clara? And Einstein? And Jules and Verne? Are they in the train?"

The Doc's smile faded. "Marty, I'm not here on visiting terms." He gripped the young man's shoulders and looked him in the eyes. "I'm sorry to say, but I must ask you to come with me once more, for this time, the entire _worlds _future depends on it!"

"What? Doc that's-" Marty began but he was interrupted.

"It's heavy I know." Doc said, knowing what Marty was going to say. "But you're the only one I know who can do this!"

Marty sighed. "Alright Doc. What do we have to do?"

Doc looked around frantically. "Not here. Come on Marty, in the train!" the two time-travelers hopped up into the train. Doc flipped some switches and pulled some levers. Just like that day in 1985, the train lifted up and flew off. It began shooting sparks into the sky, and a portal opened. When they emerged, they were no longer in hill valley. Marty looked around him. Everything looked alien. The sky itself radiated with every color known to man. As far as the eye could see there were beaches. But instead of the golden beaches of the earth that Marty knew, this sand looked silver and refined. The water seemed a blood red color, instead of the deep navy blue Marty knew.

"Doc…where the hell are we?" Marty asked

"It will all be explained when we get back to the station." Doc said, focusing on the train tracks in front of them.

A few minutes later, they pulled up in front of a small building. Doc quickly showed Marty inside and they sat down in a small room.

"Doc what's going on?" Marty asked as he noticed a middle-aged Japanese man walking into the room.

"Emmet your back. Excellent." Said the man.

"Yes, I am. And I brought Marty with me." Doc said, standing and shaking the man's hand, greeting him like an old friend.

"Doc who is this guy?" Marty asked, confused beyond belief.

"Marty this is The Station Master, a colleague of mine who also studies time travel. Together he and I have discovered many wonderful things! …But also one horrifying truth. Marty we need your help" Doc said, bowing his head.

"With what? Doc what's going on?" Marty asked frantically.

"Allow me to explain." said The Station Master "You see Marty, Emmett and I have discovered this dimension through the use of his Jules Verne Train. You noticed the brief instances between the entry and exit when you time traveled? You were briefly driving through this dimension; the Sands of Time."

"This dimension" Doc continued "is what allows time travel to exist. It has routes to every future possibility in existence. If the future is rewritten, then the main route changes. And we have also discovered why you and I always remember what different futures there have been. You see Marty; there exists a specific combination of genes that makes you and I immune to the ripple effect. People like ourselves with these genes we have come to call 'Singularity Points'. If their future ceases to exist, they live on…alone. Forever."

"Immune? But Doc, when I first went back to 1955 I started fading away." Marty protested

"That's what I thought as well. But it turns out you were merely fading back to our reality. Or what was left of it, anyway." Doc explained

"That's why we need you Marty. Your unique ability makes you perfect for combating Biff." The Station Master explained

"Biff? He's a push-over now that my dad stands up to him." Marty said

"Not that Biff." Doc said "The corrupt, powerful, gambling Biff from the alternate, hellish 1985 we saw. You see Marty, Biff is also a singularity point. And sometimes, when the future of a singularity point ceases to exist, their souls merge with the sands of time and travel back to the past to try and change reality so that their future exists once again. But merging with the sands of time has horrifying effects on their minds and bodies. Their bodies disintegrate, but they gain the ability to enter a person's mind and create a new, supernaturally powerful body out of the imagination of their host. As such, we have begun to call these creatures Imagin. However, the effect of merging with the Sands warps their mind. They come to the conclusion, which somehow has proven to be right, that wonton destruction recreates their future. But the only way they can get to that past is by offering someone a contract to change their life. The Imagin will complete that contract by their terms, often to the horror of the contract holder. Once the contract is complete, a memory within the contract holder opens a portal to the past, which the Imagin then enters. Once through the portal, they go on a rampage. The corrupt Biff from the alternate 1985 has become an Imagin. We believe he intends to use the push-over Biff you know as his host, offer him a contract, then return to 1955 once again to wreak havoc"

"That's heavy doc…but what the hell am I supposed to do about it?" Marty asked

"We have figured out a way to harness the sands in a way that does not affect the mind, body, or soul." Doc said and slid a belt, a train pass, and a case to hold the pass across the table to Marty. The belt was sleek and silver. A silver motion detector was divided into three pieces by 3 golden lines on top of the detector's screen. Beside the touch screen were 3 buttons; one brown, one silver, and one a metallic blue.

"What is this?" Marty said.

"It is a Kamen Rider Belt." Said the Station Master. "This belt will allow you to transform into a super hero of sorts, able to defeat the coming threat. You will become Kamen Rider Flux."

"Flux?" Marty asked.

"Yes Marty" said Doc. "You see, using my flux capacitor design, we have been able to find a way to harness the power of the Sands in the form of Rider Armor. It will enhance your natural abilities and give you weaponry. All you have to do is wave this pass, which contains a very small flux capacitor, over the motion detector on the belt, which is forged from the sands. And speak the code word."

"What's the code word?" Marty asked.

"Henshin!" said the Station Master

"…Henshin?" Marty asked

"Yes…it's the Japanese word for transformation. It seemed appropriate to us." Said Doc.

"Okay then. What are these colored buttons for?"

"From the start you can access the basic Plat Form. Those buttons are your form changes. Each one accesses different abilities you used during your travels with Emmet. The blue button accesses your basic form, the lightning-powered Flux Form. The brown button accesses the western Gunslinger Form. And the silver button accesses the futuristic Bionic Form. "

An alarm went off and Biff appeared on the screen, polishing a car in his shop. A yellow orb of light flew into his back. Sand then poured from his mouth and started solidifying. Before Marty could make out the details, Doc shut off the screen. "Great Scott! It's happening sooner than we thought. Marty, we have to get on the train. Biff will strike soon. You have to stop him before he fulfills that contract!"

Marty nodded and he and doc darted through the doors and onto the train. The train accelerated through the sands and returned to 1985, on the train tracks. Marty darted towards the auto shop as fast as he could. He saw Biff in his typical track suit but he also saw the creature now fully formed. It was blue and had an expensive cigar clamped between its fangs. It was a deep navy blue and had no nose. It had black horns coming out of its head and was covered in golden markings. Over its body, it wore a navy blue robe. The creature looked Biff in the eye.

"Well butthead do you have a wish or don't you?" it asked

Biff smiled and said "Yes I do. I wish that Lorraine Baines…Lorraine McFly… was mine."

The Biff Imagin laughed "Great minds…or identical ones for that matter…do think alike."

The Imagin turned to leave and saw Marty standing there. "You…you cost me my future. My entire EXISTENCE! Now I can get you back."

The creature raised its hand and a .50 caliber revolver appeared in its hand. As the Imagin took aim Marty dodge rolled and strapped on his belt. He pressed the silver button and the guitar riffs from _Johnny B. Goode_ started echoing from the belt. He took out his rider pass and looked at it.

'_You've never steered me wrong before Doc…' _Marty thought. He stood and held the pass at the ready.

"Henshin!" he called out as he swiped the pass in front of the motion detector.

**FLUX FORM**

As the voice of the belt bellowed, square shards of light scattered from the motion detector then collected on Marty's body and solidified into the black body suit known as Plat Form. Then, more armor appeared. It spun and attached itself to Marty's torso. The plates ran up Marty's torso to his neck with edged shoulder plates. The plating was a deep blue with dark blue lightning patterns echoing up the armor. Finally, a small version of the DeLorean rode over Marty's face. It separated, reconfigured, and snapped into place. Marty's helmet was now silver plated, with small versions of the DeLorean's exhaust ports serving as a visor. Marty was in awe at his power, but snapped into the situation at hand. He smirked and looked up at the Biff Imagin. A phrase was etched into his mind, and before he knew it, he felt the urge to say it.

"It's time for me to change history."

Marty rushed at the Biff Imagin with surprising speed and landed a right hook on his face. The Imagin stumbled and took aim, firing at Marty. Marty dodged and made his way backward. Marty stood and took out his pass.

"I can't get up close with him having that gun…better try one of my other options." Marty said. He pushed the brown button on the belt and the western music from the Hill Valley Fair he and Doc attended in 1885 began playing. Marty smirked as he swiped the pass over the motion detector.

**GUNSLINGER FORM**

Marty's blue Flux Form armor vanished as he reverted to plat form. Two cow catchers appeared, flipped upside down, and attached to Marty's shoulders. A piece of armor resembling a brass colored version of the door Marty had used as a bulletproof vest in his fight against Mad Dog Tannen fastened itself onto his torso. 2 small cow catchers railed down Marty's helmet. One fastened itself to the mouthpiece. The other split into two and wrapped itself around the eyes, becoming a slitted visor. Once again, a phrase was etched into his mind.

"I better warn you" Marty said. "I'm a crack shot."

Marty drew a revolver from a holster on the side of his belt and fired, surprised to find it fired energy bolts. The first bolt hit the Biff Imagin in the chest, knocking it off balance. Marty fired a few more times, causing the Imagin to start firing back. The street turned into an all out shootout. Suddenly Marty heard Doc's voice in speakers in the helmet.

"Marty! You have to weaken him some to get that gun away from him! Swipe the pass in front of the detector again to initiate Full Charge. Your pistol will fire a large blast called the Peacemaker Blast."

"Got it Doc"

Marty dodged a blast from the Imagin and swiped his pass.

**FULL CHARGE**

Marty held the gun with both hands and took aim at the gun in the Imagin's hand.

"PEACEMAKER BLAST!" Marty yelled as a large blue orb of energy fired and incinerated the Imagin's forearm. The recoil from the shot knocked Marty back a few steps, but he remained standing. The Imagin howled in pain as sand poured from the stub where his arm was. Soon, the arm reformed, and the Imagin, more furious than ever, summoned a new weapon; a cane sword.

Marty dodged several quick swings from the new melee weapon before diving behind a car.

"DOC! Please tell me I have some sort of melee weapon!" Marty pleaded.

"Of course Marty! Switch to Bionic Form!" Doc replied.

Marty stood and pressed the silver button. An adventurous theme (A/N: the Back to the Future theme song) rang out from the belt and Marty swiped the pass again.

**BIONIC FORM**

The armor of Gunslinger Form faded and was soon replaced. A reinforced rectangular chest plate and two rounded shoulder pieces attached themselves to Flux. The chest piece was sliver with green lines covering it, similar to a microchip. The shoulder pieces were green with black ones and zeroes integrated into the design. Copper wires ran across the mouthpiece and then a black dish with circuit patterns fastened itself on as the visor for this form. A silver bat similar to Griff's appeared in Flux's hand and grew to full size.

Marty walked slowly towards the Imagin. It swung his cane but Marty dodged and clubbed him upside the head with his titanium baseball bat. The Imagin stumbled back then got hit again, then one more time. The Imagin stumbled to get up but Marty kicked it down. The Imagin yet again stumbled to his feet. It started to swing, but Marty blocked the blow. Marty took out his Rider Pass and once again swiped it.

**FULL CHARGE**

"BATTER UP!" Marty yelled. The bat coursed with energy as Marty kicked the Biff Imagin back and swung the bat, shattering the sword and knocking the Imagin back 12 feet.

"Marty!" Doc said through the communicator. "Finish him off! Switch back to Flux Form and use Full Charge!"

Marty did as he was told, pressing the blue button and swiping the pass twice.

**FLUX FORM**

**FULL CHARGE**

As the Flux armor appeared on him, Marty's right leg began to charge with electricity. As the Biff Imagin stumbled to its feet again, Marty leaped into the air as electricity coursed to the ball of his foot. Marty executed a downward flying side kick toward the Imagin. As he descended, electricity trailed behind Marty resembling a lightning bolt.

"LIGHTNING KICK!" Marty screamed as he neared the Imagin.

The kick connected and the Biff Imagin howled in pain before exploding. Marty landed, panting. He removed the belt and the armor faded away. He looked at Biff, who stood in awe.

"I didn't see a thing" Biff said, stuttering.

"Damn right you didn't" Marty said.

As if on cue, the Time Train drove in front of Marty, and he started to hop on board, but soon realized the ashes from the Biff Imagin where gathering and replicating. It formed into a gigantic snake, an embodiment of the greed Biff had so long let fester in his heart. This was Biff's Gigandeath form. The Gigandeath: Avarice. The giant snake hissed at Marty, who had already strapped on the belt and raised his pass

"HENSHIN!" he cried and swipes the pass. But as he did, he saw Doc's time train crash into the face of the Gigandeath, and explode, destroying the beast. Doc jumped from the train.

"MARTY!"

"DOC!"

**FLUX FORM**

Like lightning, Marty ran and caught Doc Brown in the nick of time. He set down his old friend and once again removed the belt.

"Doc…the train…you can't travel through time anymore." Marty said sadly

"Marty. You forget that in the Sands, time is warped." The doc said.

A train whistle, playing whimsical notes, echoed around them. A portal to the sands opened and train tracks built themselves in front of Marty and the Doc. A bullet train sped out and stopped on a dime.

"This is the Den-Liner. A much more improved model of my old time train…now according to our research, Marty, the Imagin won't appear again until the year 2007. Will you travel with us there?" The Doc asked

"Sure. Back and forth trips could be fun." Marty said.

"Marty…fighting these creatures would be a full time job. You wouldn't be back until you'd aged into your 20's." the Doc said, solemnly.

Marty stared at his belt. "Then no Doc. I love my life here. I think I've had enough adventure for a lifetime…but if you really need me, you know where to find me."

"Well then, I'll let the Station Master pick out a successor." Doc said

The station manager appeared in the door of the Den-Liner standing next to a rider similar to Flux. He spoke in a calm voice. "I already have."

The chest armor of this Rider was shaped like Flux's but instead of the blue lightning patterns, it was solid red with silver outlines. The eyepieces looked like a peach split in half, and the belt had 4 buttons next to its logo. The rider hopped down from the train and spoke in a confident voice as he walked up to Marty.

"So this is my predecessor, eh old man?" the Rider asked. "Well, Flux; I am Kamen Rider Den-O. ORE, SANJOU!" he struck a pose in front of Marty then another voice peeped out from the helmet.

"Momotaros…don't act so brash. We have much more experience then he will." Said the voice.

"Oi Ryutaro, don't ruin my entrance!" said Den-O's main voice, now identified as Momotaros.

Marty laughed. "You seem like you're going to do fine, Den-O." Marty shook hands with this new Rider, the meeting of two generations. Marty removed his belt and pass and handed them to Doc as his armor faded away. Doc handed back the pass.

"Just in case you want to pop in…we built a compound in the Sands. Hold the pass in your hand and walk through any door when all 3 hands on a clock meet and you'll wind up on the Den-Liner." Doc said "We'll appoint an Owner for the train, and he can take you to my office."

"I will Doc. I promise." Marty said, embracing his old friend and mentor.

Doc and Den-O boarded the Den-Liner, which sped into the future. Marty smiled as he gripped the pass in his hands and walked back to the train tracks. He could see his mentor whenever he liked now, and might even have more adventures now. Bigger adventures than ever before.

**End.**

A/N: That's that! I've had this idea since before I started writing rider Fanfics, and decided to write it now. It's a one-shot for now, but I may build on it if I feel and/or people like this fic. Well, that's all for now folks! Read and review, flames are ignored!


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